As many as 27,000 people live per square kilometre in Mumbai, making the metro one of the densest cities in Asia, as per the Asian Green City Index.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/mumbai-densest-city-asia
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/indian-express-mumbai
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/energy-efficiency
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/india
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/mumbai
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/maharashtra
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/habitat-and-urbanisation
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sewage
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environment
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/alternative-fuels
[12] http://admin.indiaenvironmentportal.org.in/category/thesaurus/infrastructure-development
[13] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sustainable-development
[14] http://admin.indiaenvironmentportal.org.in/category/thesaurus/population